This invention relates to a manual transmission and, more particularly, to a manual transmission for a front-engine front-wheel (FF) drive vehicle having a transversely mounted engine.
In an FF drive vehicle having a transversely mounted engine, a more compact transmission is sought to deal with vehicles that are more compact, engines that have greater numbers of cylinders and transmissions have multiple speeds. The overall length of the transmission is a particularly important factor since it has a major influence upon the handling of the vehicle, e.g., the turning radius thereof. Demand for improved operability also has been increasing in recent years and addition of a synchronizer for reverse gear is sought. Accordingly, a manual transmission according to an example of the prior art disclosed in the specification of WO 97/13990 has a synchronizer Rs for reverse gear disposed on a second intermediate shaft 112, as illustrated in FIG. 3. The structure of the manual transmission according to this example of the prior art will now be described in detail.
As shown in FIG. 3, first and second intermediate shafts 111 and 112, respectively, are disposed in parallel with an input shaft 110 and an output shaft 113. Gear trains I, II, III and IV for first, second, third and fourth speeds, respectively, are provided extending between the first input shaft 110 and the first intermediate shaft 111, and gear trains V and VI for fifth and sixth speed, respectively, provided extending between the input shaft 110 and the second intermediate shaft 112. A reverse gear R is constituted by a first-speed driving gear 100a on the input shaft 110, a first-speed driven gear 100b on the first intermediate shaft 111, a reverse-only driving gear Ra integrated with the first-speed driven gear 100b, a reverse-only driven gear Rb and the reverse-gear synchronizer Rs on the second intermediate shaft 112. Furthermore, a firstxe2x80x94second-speed synchronizer 111S1 and a thirdxe2x80x94fourth-speed synchronizer 111S2 are disposed on the first intermediate shaft 111, and the reverse-gear synchronizer Rs and a fivexe2x80x94sixth-speed synchronizer 112s are disposed on the second intermediate shaft. No synchronizer, however, is disposed on the input shaft 110.
In a case where a synchronizer is added onto reverse gear in order to improve operability, a problem which arises is an increase in the overall length of the manual transmission. If the reverse-only driving and driven gears Ra, Rb, namely a total of two gears, are disposed on the first and second intermediate shafts 111, 112, as in the manual transmission proposed by the specification of WO 97/13990, as illustrated in FIG. 3, the axial lengths of the first and second intermediate shafts 111, 112 are increased by amounts equivalent to the gears Ra and Rb. The problem that results is an increase in the overall length L of the manual transmission.
Accordingly, an object of the present invention is to provide a manual transmission having a small overall length even though a synchronizer is provided exclusively for reverse gear.
Another object of the present invention is to provide a compact manual transmission having a small overall length especially for use in FF drive vehicles.
According to an aspect of the present invention, at least one of the foregoing object is attained by providing a manual transmission comprising an input shaft; first and second intermediate shafts disposed in parallel with the input shaft; and a reverse-gear stage; wherein the reverse-gear stage includes: a low-speed driving gear disposed on the input shaft; a low-speed driven gear disposed on the first intermediate gear for meshing with the low-speed driving gear; a reverse-only driving gear disposed on the first intermediate shaft; a synchronizer for reverse gear disposed on the first intermediate shaft or reverse-only driving gear for causing the low-speed driven gear and the reverse-only driving gear to engage and disengage; and an intermediate-speed driven gear disposed on the second intermediate shaft for meshing with the reverse-only driving gear.
In the manual transmission according to the present invention, a prescribed gear among the low- and intermediate-speed gears functions also as a gear for reverse, as a result of which the number of reverse-only gears which function solely in reverse gear is reduced. By thus reducing the number of reverse-only gears, the lengths of the input shaft and of the first and second intermediate shafts in this manual transmission are reduced, as a result of which the overall length of the manual transmission is diminished. This also makes it possible to reduce the number of component parts of the manual transmission as well as the manufacturing cost of thereof.
According to another aspect of the present invention, there is provided a manual transmission comprising: an input shaft; first and second intermediate shafts disposed in parallel with the input shaft; a first-speed driving gear, a second-speed driving gear, a third-speed driving gear, a fourth-speed driving gear, a fifth driving gear and a six-speed driving gear disposed on the input shaft; a reverse-only driving gear, a first-speed driven gear and a second-speed driven gear disposed on the first intermediate shaft; a third-speed driven gear, a fourth-speed driven gear, a fifth-speed driven gear and a sixth-speed driven gear disposed on the second intermediate shaft; a thirdxe2x80x94fourth-speed synchronizer disposed on the first input shaft for selectively engaging and disengaging the third-speed driving gear or the fourth-speed driving gear with said input shaft; a synchronizer for reverse gear disposed on the first intermediate shaft or reverse-only driving gear for causing the first-speed driven gear and the reverse-only driving gear to engage and disengage; a firstxe2x80x94second-speed synchronizer disposed on the first intermediate shaft for selectively engaging and disengaging the first-speed driven gear or the second-speed driven gear with the first shaft; and a fifthxe2x80x94sixth-speed synchronizer disposed on the second intermediate shaft for selectively engaging and disengaging the fifth-speed driven gear or the sixth-speed driven gear with the second intermediate gear; wherein a reverse-gear stage is constructed by the first-speed driving gear, the first-speed driven gear, the reverse-only driving gear, the third-speed driven gear and the synchronizer for reverse gear.
In a preferred embodiment of the present invention, the reverse-gear stage of the manual transmission includes a first-speed driving gear, a first-speed driven gear and a third-speed driven gear.
In a preferred embodiment of the manual transmission, an intermediate-speed synchronizer, a low-speed synchronizer and a high-speed synchronizer are disposed on the input shaft, the first intermediate shaft and the second intermediate shaft, respectively. By thus disposing a plurality of synchronizers on respective shafts in dispersed fashion, the axial length of each shaft can be reduced overall.
In a preferred embodiment of the manual transmission, the low-speed driven gear constituting reverse gear has one gear piece capable of engaging the synchronizer for reverse gear, and another gear train constituting intermediate or high speed is situated between the gear body of the low-speed driven gear and the one gear piece along the axial direction thereof.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.